The subject invention generally relates to ink jet printing, and more particularly to a narrow thin film ink jet printhead.
The art of ink jet printing is relatively well developed. Commercial products such as computer printers, graphics plotters, and facsimile machines have been implemented with ink jet technology for producing printed media. The contributions of Hewlett-Packard Company to ink jet technology are described, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985); Vol. 39, No. 5 (October 1988); Vol. 43, No. 4 (August 1992); Vol. 43, No. 6 (December 1992); and Vol. 45, No. 1 (February 1994); all incorporated herein by reference.
Generally, an ink jet image is formed pursuant to precise placement on a print medium of ink drops emitted by an ink drop generating device known as an ink jet printhead. Typically, an ink jet printhead is supported on a movable print carriage that traverses over the surface of the print medium and is controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to a pattern of pixels of the image being printed.
A typical Hewlett-Packard ink jet printhead includes an array of precisely formed nozzles in an orifice plate that is attached to an ink barrier layer which in turn is attached to a thin film substructure that implements ink firing heater resistors and apparatus for enabling the resistors. The ink barrier layer defines ink channels including ink chambers disposed over associated ink firing resistors, and the nozzles in the orifice plate are aligned with associated ink chambers. Ink drop generator regions are formed by the ink chambers and portions of the thin film substructure and the orifice plate that are adjacent the ink chambers.
The thin film substructure is typically comprised of a substrate such as silicon on which are formed various thin film layers that form thin film ink firing resistors, apparatus for enabling the resistors, and also interconnections to bonding pads that are provided for external electrical connections to the printhead. The ink barrier layer is typically a polymer material that is laminated as a dry film to the thin film substructure, and is designed to be photodefinable and both UV and thermally curable. In an ink jet printhead of a slot feed design, ink is fed from one or more ink reservoirs to the various ink chambers through one or more ink feed slots formed in the substrate.
An example of the physical arrangement of the orifice plate, ink barrier layer, and thin film substructure is illustrated at page 44 of the Hewlett-Packard Journal of February 1994, cited above. Further examples of ink jet printheads are set forth in commonly assigned U.S. Pat. No. 4,719,477 and U.S. Pat. No. 5,317,346, both of which are incorporated herein by reference.
Considerations with thin film ink jet printheads include increased substrate size and/or substrate fragility as more ink drop generators and/or ink feed slots are employed. There is accordingly a need for an ink jet printhead that is compact and has a large number of ink drop generators.
One aspect of the present invention provides an inkjet printhead including a printhead substrate having a plurality of thin film layers. The printhead includes four side by side columnar arrays of drop generators formed in the printhead substrate and extending along a longitudinal extent. Each columnar array of drop generators has at least 100 drop generators. The four columnar arrays of drop generators comprise a first columnar array and a second columnar array separated from each other by at most 630 micrometers, and a third columnar array and a fourth columnar array separated from each other by at most 630 micrometers. The printhead includes four columnar arrays of FET drive circuits formed in the printhead substrate respectively adjacent the columnar arrays of drop generators for energizing the columnar arrays of drop generators.
Another aspect of the present invention provides an ink jet printhead including a printhead substrate having a plurality of thin film layers. The printhead includes four side by side columnar arrays of ink drop generators formed in the printhead substrate and extending along a longitudinal extent. Each columnar array of ink drop generators has ink drop generators that are separated by an ink drop generator pitch P. The ink drop generators produce ink drops having an ink drop volume that enables single pass printing of a resolution that is 1/(4P) dpi along a print axis parallel to the longitudinal extent. Each of the ink drop generators includes a heater resistor having a resistance of at least 100 ohms. The printhead includes four columnar arrays of FET chive circuits formed in the printhead substrate respectively adjacent the columnar arrays of ink drop generators for energizing the columnar arrays of ink drop generators. The printhead includes power traces connected to the ink drop generators and the FET drive circuits. The FET drive circuits are configured to compensate for a variation in a parasitic resistance presented by the power traces.